CN105668575B - A kind of technique for preparing mesopore silicon oxide using Si-Al zeolite and recycling aluminium - Google Patents

Abstract

The present invention relates to the field of resource utilization of silica-alumina zeolite and the preparation of mesoporous silica materials, in particular to a new technology for comprehensive resource utilization of silica-alumina preparation of mesoporous silica materials and extraction of aluminum elements in silica-alumina zeolite, comprising the following steps: React the silica-alumina zeolite with an acid solution, completely destroy the crystal structure of the zeolite through acid treatment, leach the metal elements in its composition, and then separate the solid and liquid to obtain a solid phase and an acid solution containing aluminum; the solid phase is washed and dried, that is The obtained mesoporous silicon oxide material has a specific surface area of 580-800 m ² /g and a most probable pore diameter of 3.5-4.5 nm, and the aluminum-containing acid solution obtained after filtering is used for extracting aluminum.

Description

A process for preparing mesoporous silica and recovering aluminum by using silica-alumina zeolite

technical field

The invention relates to the fields of resource utilization of silica-alumina zeolite and preparation of mesoporous silicon oxide materials, in particular to a new technology for resource utilization and comprehensive utilization of silica-alumina zeolite for preparing mesoporous silica materials and extracting aluminum elements in silica-alumina zeolite.

Background technique

Due to its excellent pore size distribution (2-50nm) and large specific surface area, mesoporous materials have been widely used in many aspects such as adsorption, separation, catalysis, drug embedding and delivery. Mesoporous silica is one of the largest families of inorganic materials in mesoporous materials. With its high specific surface area, excellent thermal stability, good hydrothermal stability, abundant surface acid-base sites and thick pore wall And other characteristics, has been widely used in adsorption separation, catalysis, ion exchange, micro-reaction and other fields, with high added value.

At present, the preparation of mesoporous materials mainly adopts the template method. The template method refers to the use of surfactants (soft templates) or some mesoporous materials (hard templates) as pore-forming agents or skeleton structures and chemical raw materials to form intermediates, and then obtain mesoporous structures by removing template components. However, in order to ensure the stable formation and high order of soft templates, there are high requirements on the purity and types of templating agents, raw materials, and solvents. These templating agents, raw materials and solvents are not only expensive, but some (such as ethyl silicate, methanol, benzene) are even toxic and harmful. The subsequent organic template calcination removal process will increase the complexity of the process, and cause environmental pollution and waste of templates. The hard template method mostly uses the ordered material (ordered mesoporous silica or mesoporous carbon) synthesized by the soft template method as a hard template, and then removes the hard template to prepare the target mesoporous material. Obviously, the hard template method has a higher cost. The high cost limits the industrial application of the template method.

Obviously, the process of preparing mesoporous materials without templates and template materials and using cheap and easy-to-obtain mineral materials as raw materials, that is, the process of preparing mesoporous materials by using mineral materials without templates, can reduce the production cost of mesoporous materials and promote mesoporous materials. The industrial application of materials provides a new research direction for the comprehensive utilization of natural and easy-to-obtain mineral materials.

Most natural minerals contain high silica-alumina components, which have the potential to prepare high value-added mesoporous silica materials. On the other hand, aluminum is an important basic raw material for life and industry, and a basic material that is widely used and has an important social status. Therefore, if a simple and low-cost process technology for preparing mesoporous silica materials from natural minerals and extracting aluminum can be explored, it will greatly promote the resource utilization of natural minerals.

Contents of the invention

The purpose of the present invention is to provide a low-cost, simple process for the comprehensive utilization of silica-alumina zeolite resources and a new technology for preparing mesoporous silica, that is, a new technology for preparing mesoporous silica materials using silica-alumina zeolite and extracting aluminum.

In order to achieve the above object, technical scheme of the present invention is:

A process for preparing mesoporous silicon oxide and recycling aluminum by using silica-alumina zeolite, comprising the following steps:

React the silica-alumina zeolite with an acid solution, completely destroy the crystal structure of the zeolite through acid treatment, leach the metal elements in its composition, and then separate the solid and liquid to obtain a solid phase and an acid solution containing aluminum; the solid phase is washed and dried, that is The obtained mesoporous silicon oxide material has a specific surface area of 580-800 m ² /g and a most probable pore diameter of 3.5-4.5 nm, and the aluminum-containing acid solution obtained after filtering is used for extracting aluminum.

The main purpose of the acid treatment process is to completely destroy the crystal structure of zeolite, leach metal elements such as sodium and aluminum in its composition, and obtain mesoporous materials. The acid solution used should be able to destroy the crystal structure of zeolite, and it can be one or a mixture of two or more in a strong acid (such as HCl, HNO ₃ , H ₂ SO ₄ , etc.) solution in any proportion, or a strong acid solution A mixture of (one or more) and other weak acids (such as acetic acid, HNO ₂ ) in an appropriate ratio. It should be noted that if the silica-alumina zeolite contains more calcium and barium elements, the use of acid solutions containing sulfate radicals is not recommended, because the formation of CaSO ₄ and BaSO ₄ precipitates that are insoluble in strong acids will lead to the formation of mesopores. Silica purity decreases.

The acid solution is a 1-10 mol/L HCl solution, the zeolite and the HCl solution are reacted at 40-100°C for 2-12 hours, and the solid-to-liquid ratio is 1kg:4-50L.

The present application does not have very strict requirements on the grade of the silica-alumina zeolite, but if the silica-alumina zeolite contains solid substances that cannot be dissolved in strong acids, the specific surface area of the obtained mesoporous silica will be reduced. In other words, the impurity components in the silica-alumina zeolite that are soluble in strong acid do not have much influence on the grade of the obtained mesoporous silica.

In this field, zeolite is a common microporous material (pore diameter less than 2nm). In terms of crystal structure, it is shared by four corner vertices of [SiO ₄ ] tetrahedron and [AlO ₄ ] tetrahedron and along the three-dimensional space connected, and eventually become a frame-like crystal. Unlike other framework aluminum silicates, zeolites have secondary structural units that form polyhedral spaces of a certain shape in the zeolite crystal structure, the so-called cages (eg, α-cage, β-cage, γ -cage). Therefore, zeolite has a relatively high specific surface area (400-800m ² /g), and is widely used in the fields of adsorption, catalysis, separation, ion exchange and the like. However, with the continuous development of science, the application of traditional mineral silica-alumina zeolite is more and more restricted, and its main defects are: (1) The pores of zeolite are of micropore size (mostly less than 1nm) and are not applicable (2) Although most mineral silica-alumina zeolites have a relatively perfect crystal structure, their acid stability and thermal stability are very low due to their relatively high aluminum content. Therefore, the research and development of highly stable mesoporous materials is an important branch in the field of inorganic materials. Mesoporous materials (especially mesoporous silica and mesoporous carbon) have high specific surface area, rich pore structure, relatively uniform mesoporous pore size distribution (2-50nm), and high thermal and acid stability. , It has a wider role in the adsorption and separation of macromolecules, which is difficult for many microporous zeolite molecular sieves, especially in catalytic reactions. In addition, it cannot be denied that zeolite has a rich pore structure precisely because of its special crystal structure. Once the crystalline structure of zeolite is completely destroyed, the microporous pore structure inside the zeolite will inevitably collapse, resulting in its application value. loss. In fact, scientific researchers have carried out the work of modifying the structure of silica-alumina zeolite a long time ago, but all of them were carried out under the premise of ensuring the zeolite crystal framework, that is, to properly dealuminate the silica-alumina zeolite molecular sieve, so that the original zeolite framework Bits produce mesoporous channels. These mesoporous channels are obtained due to local dealumination of the molecular sieve framework and in-situ generation of cavities. The size and number of the pores are related to dealumination conditions and are difficult to control. In short, there is currently no research or report on completely destroying the crystal structure of zeolite, etching out the aluminum component, and obtaining mesoporous silica materials. However, the present application made breakthroughs in thinking and technological innovation, and creatively proposed a process for acid treatment of silica-alumina zeolite, that is, acid-treating silica-alumina zeolite with only micropore structure but no mesopore structure. The present application does not have very strict requirements on the taste of the silica-alumina zeolite, so any existing silica-alumina zeolite can be used. The main purpose of the acid treatment process is to completely destroy the crystal structure of zeolite, leach the metal elements in its composition, and obtain mesoporous materials. The acid solution used should be able to destroy the crystal structure of zeolite, and it can be a mixture of one or more than two kinds of strong acid solution in any proportion, or a mixture of strong acid solution and other weak acids in proper proportion.

Compared with the prior art, the present invention has the following advantages:

1. Use silica-alumina zeolite as raw material to prepare amorphous mesoporous silica, without using expensive templates or template materials (such as hexamethylenediamine, hexadecyltrimethylammonium bromide, etc.) in the preparation process, There is also no need to introduce any toxic and harmful organic solvents (such as benzene, methanol, ether, etc.), the production process is simple, the cost is low, and it is suitable for industrial production.

2. The preparation of mesoporous silica and the extraction of aluminum in this process depend on the acid treatment of silica-alumina zeolite. After the silica-alumina zeolite is treated with acid, its internal crystal structure is completely destroyed, and a large amount of aluminum elements are etched to obtain mesoporous silicon oxide and aluminum-containing acidic leaching solution. The acidic leaching solution containing aluminum can be used to extract aluminum to prepare metallic aluminum or mesoporous alumina.

3. The practicability of this process is very strong, which is mainly based on the following points: a, silica-alumina zeolite, especially silica-alumina zeolite containing sodium and calcium, has a large content in nature and is easier to prepare by artificial synthesis; b. After the silica-alumina zeolite is treated with acid, its crystal structure is completely destroyed, the aluminum in its composition is etched into the acid solution, and the silicon oxide component insoluble in the acid solution will form an amorphous mesoporous oxidation with a high specific surface area. Silicon—this is a new technology for preparing mesoporous silica with high specific surface area; c. After the silica-alumina zeolite is treated with acid, the aluminum in its composition is etched into the acid solution, which can be separated from the silicon oxide component that is insoluble in acid , so that it can be used to extract aluminum; d, this process relies on the joint action of strong acid solution and silica-alumina zeolite, and the metal ions (such as: Na, K, Ca, Ba, Sr, Mg) in the silica-alumina zeolite will The zeolite crystal structure is completely destroyed and dissolved in a strong acid solution, which can be separated from the acid-insoluble silicon oxide components, and these metal elements can be extracted through appropriate processes.

4. The mesoporous silica prepared by this process has a relatively high specific surface area of 580-800m ² /g, and its most probable pore diameter is 3.5-4.5nm, which is much larger than the original micropore pore diameter of silica-alumina zeolite (<2nm). . The mesoporous silica has a good adsorption effect on methylene blue, can be used as an excellent adsorption material, and has a wide application prospect.

Description of drawings

Fig. 1 is the nitrogen adsorption-desorption isotherm diagram of mesoporous silicon oxide in Example 1;

Fig. 2 is a pore size distribution diagram of the mesoporous silica in Example 1 analyzed by using the BJH model.

Detailed ways

In order to enable those skilled in the art to better understand the technical solutions of the present invention, the present invention will be further described in detail below in conjunction with the accompanying drawings.

Example 1

A new technology for the comprehensive utilization of silica-alumina zeolite resources and the preparation of mesoporous silica, which comprises the following steps:

Mix 13X silica-alumina zeolite molecular sieve with 5mol/L HCl solution at a ratio of 1kg:20L, stir and react at 80°C for 6h, then filter and wash the obtained solid product with deionized water until neutral, and then pass through 110 ℃ drying to remove water, to obtain the mesoporous silicon oxide material prepared by the template-free method. The aluminum-containing acidic leaching solution obtained after filtration can be used to extract aluminum and prepare metallic aluminum or mesoporous alumina.

The specific surface area of the mesoporous silicon oxide material obtained in this example is 790 m ² /g, and its most probable pore diameter is 3.8 nm. The nitrogen adsorption-desorption isotherm and the pore size distribution obtained according to the BJH model are shown in Figure 1 and Figure 2.

Example 2

A new technology for the comprehensive utilization of silica-alumina zeolite resources, which comprises the following steps:

Mix 4A silica-alumina zeolite molecular sieve with 5mol/L HCl solution at a ratio of 1kg:20L, stir and react at 80°C for 6h, then filter and wash the obtained solid product with deionized water until it is neutral, and pass through 110 ℃ drying to remove water, and obtain a mesoporous silica material prepared by a template-free method. The aluminum-containing acidic leaching solution obtained after filtration can be used to extract aluminum.

The specific surface area of the mesoporous silicon oxide material obtained in this example is 751 m ² /g, and its most probable pore diameter is 3.9 nm.

Claims (1)

1. A process utilizing silica-alumina zeolite to prepare mesoporous silicon oxide and reclaim aluminum, is characterized in that comprising the following steps: React the silica-alumina zeolite with an acid solution, completely destroy the crystal structure of the zeolite through acid treatment, leach the metal elements in its composition, and then separate the solid and liquid to obtain a solid phase and an acid solution containing aluminum; the solid phase is washed and dried, that is The obtained mesoporous silicon oxide material has a specific surface area of 580-800m ² /g and a most probable pore diameter of 3.5-4.5nm; the aluminum-containing acid solution obtained after filtration is used to extract aluminum; The acid solution is a 1-10 mol/L HCl solution, the zeolite and the HCl solution are reacted at 40-100°C for 2-12 hours, and the solid-to-liquid ratio is 1kg:4-50L.